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Each MariaDB table is associated with a particular storage engine. InnoDB tables have particular physical and logical characteristics that affect performance, scalability, backup, administration, and application development.

In terms of file storage, each InnoDB table is either part of the single big InnoDB system tablespace, or in a separate .ibd file if the table is created in file-per-table mode. The .ibd file holds data for the table and all its indexes, and is known as a tablespace.

InnoDB tables created in file-per-table mode can use the Barracuda file format. Barracuda tables can use the DYNAMIC row format or the COMPRESSED row format. These relatively new settings enable a number of InnoDB features, such as compression, fast index creation, and off-page columns

For backward compatibility with MariaDB 5.1 and earlier, InnoDB tables inside the system tablespace must use the Antelope file format, which supports the compact row format and the redundant row format.

The rows of an InnoDB table are organized into an index structure known as the clustered index, with entries sorted based on the primary key columns of the table. Data access is optimized for queries that filter and sort on the primary key columns, and each index contains a copy of the associated primary key columns for each entry. Modifying values for any of the primary key columns is an expensive operation. Thus an important aspect of InnoDB table design is choosing a primary key with columns that are used in the most important queries, and keeping the primary key short, with rarely changing values.

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